A firearm discharges a cartridge to fire a bullet by striking the primer of the cartridge with a firing pin positioned within the bolt of the firearm. The primer is ignited by striking it with sufficient force. The ignited primer ignites gunpowder in the cartridge to propel the bullet toward a target.
The firing pin is driven toward the primer along a firing pin well in the bolt. For example, a spring-loaded hammer strikes a head of the firing pin and drives it along the firing pin well toward the cartridge primer. A striker point at one end of the firing pin strikes the primer to ignite it and fire the cartridge.
M16 /AR-15 rifles are used worldwide by military and law enforcement organizations and civilian sport enthusiasts. M16 and AR-15 rifles are substantially the same, except that the former is switchable between automatic and semi-automatic operation and the latter operates only in the semi-automatic mode. As a result, most of the components of M16 and AR-15 rifles, including the firing pins, are substantially the same and are preferred to as M16/AR-15 components.
FIG. 1 is a side elevation of a conventional heat-treated steel M16/AR-15 rifle firing pin 10 having at one end a cylindrical striker section 12 with a striker point 14 for striking a primer of a cartridge (not shown) and at another end a head section 16 with a head 18 that a rifle hammer hits to drive firing pin 10 against the cartridge.
Head section 16 includes a shoulder 20 with a radially outer edge 22 that is formed perpendicular to the plane of shoulder 20 for ease of manufacturability. In AR-15 rifles, shoulder 22 functions to recock the hammer as the bolt returns after a cartridge is fired. An elongate cylindrical central body section 24 is positioned between striker section 12 and head section 16. Striker section 12 and central body section 24 are of first and second diameters 26 and 28, respectively, first diameter 26 being less than second diameter 28.
Although M16/AR-15 rifles are typically quite reliable and accurate, they can suffer from some disadvantages. For example, while accurate at moderate ranges within about 300 meters, M16/AR-15 rifles are not as accurate as other weapons at ranges greater than about 300 meters.
In addition, M16/AR-15 rifles sometimes exhibit an extremely dangerous condition called "slam fire," in which the weapon inadvertently discharges when a cartridge or round is loaded into the chamber of the weapon (referred to as chambering). Incidental to the normal chambering of a cartridge, the firing pin strikes the cartridge primer with a force that is intended to be insufficient to ignite the primer. A slam fire occurs when the primer is ignited and the cartridge discharged by the incidental strike of the firing pin against the primer. It will be appreciated that slam fire can pose an extreme danger to bystanders when a cartridge is chambered in these weapons.